The invention relates to improvements in apparatus, known as door closers or door checks, which serve to control the movements of door panels or like components between first and second positions. More particularly, the invention relates to improvements in apparatus of the type wherein the movement of a component (hereinafter called door panel) toward open position is opposed by one or more springs or other suitable biasing means, and wherein a piston in the housing of the apparatus forms part of a fluid-operated damper which is operative at least while the door panel moves from closed toward open position
It is known to provide a door closer with a shaft which is rotatably journalled in an elongated fluid-containing housing and is operatively connected with a pivotable door panel. The shaft cooperates with a piston which is reciprocable in the housing so that the piston moves in the housing in response to rotation of the shaft by the door panel and vice versa. The piston divides the internal space of the housing into at least one chamber and a compartment and is provided with a check valve which permits the fluid to flow from the compartment into the chamber. The housing of such door closer defines a channel which permits the fluid to flow from the chamber into the compartment during the initial stage of pivoting of the door panel from its closed position. The channel is sealed from the chamber upon completion of the initial stage of such movement, and the rate of outflow of fluid from the chamber (in response to further pivoting of the door panel from the closed position toward the fully open position) is thereupon regulated by a throttle valve. Reference may be had to German Offenlegungsschrift No. 33 31 783 of Schnarr et al. This publication discloses a door closer wherein the housing for the reciprocable piston defines a chamber surrounding the head of the piston during a certain stage of movement of the piston relative to the housing while the door panel moves from its closed toward its open position. The chamber communicates with a channel which is provided in the housing and extends along that portion of the housing which contains a spring serving as a means for biasing the door panel to its closed position. An adjustable throttle valve in the housing controls the flow of fluid in the channel. Proper setting of such throttle valve must be selected by trial and error. As a rule, the setting of the valve is such that it brings about an insufficient or an excessive damping action by failing to adequately restrict the flow of fluid in the channel or by excessively restricting such flow. If the valve is set to fully seal or to practically seal the channel, the door panel cannot be moved beyond that (intermediate) position in which the piston is surrounded by the chamber in the housing of the door closer. Attempts to pivot the door panel beyond such intermediate position can result in damage to or in total destruction of the door closer, of the linkage between the door closer and the panel, of the means for securing the door closer to the door panel and/or of the hinge or hinges for the door panel. Attempts to overcome the drawbacks of the just described door closer include the utilization of pressure relief valves which open when the pressure in the chamber reaches a preselected maximum value. The utilization of pressure relief valves is not a satisfactory solution since they deactivate the door closer under circumstances when its controlling action is most desirable, e.g., when a person or a vehicle propels the door panel from the closed position with a great force which must be effectively resisted by the door closer.